This invention relates to optical components generally, that is, components which operate in the optical domain. Such components are designed for use in various systems which utilize optical fibers, such as optical communications systems, optical data processing systems and optical switching systems. Specifically, this invention pertains to an optical time slot interchanger.
The development of optical fiber and optical semiconductor technologies in recent years has made possible various types of optical communications systems and optical switching systems. To utilize the full bandwidth and speed available in optical systems, it has become necessary to design and fabricate optical logic and switching components which eliminate the necessity for electrical-to-optical and optical-to-electrical conversions.
With future communications networks being envisioned to have terabit capacity, light-speed transmission alone does not suffice for the full utilization of available bandwidth. Ultra-high-speed switching will also be necessary. At present, the high bandwidth advantage of optical fibers is still not fully utilized because electronic switching systems are not fast enough for high speed and high throughput optical switching. To solve this problem, the switching functions must be performed in the optical domain. Switching and multiplexing with the speed of light is necessary. Consequently, the success of terabit networks now relies on the successful development of photonic switching and signal processing systems. Since no electrical-to-optical or optical-to-electrical conversion will be allowed in these systems, pure optical subsystems, such as optical memory cells, optical shift registers, optical serial-to-parallel converters and optical parallel-to-serial converters will play important roles in these systems.
While space-division photonic switching has been successfully demonstrated, progress in time-division photonic switching is very slow. In existing optical time-division switching systems, the time slot interchange is accomplished by using the demultiplexing/storing/retrieving/multiplexing procedure. Examples may be found in R. A. Thompson and P. P. Giordano, "An experimental photonic time-slot interchanger using optical fibers as reentrant delayline memories," J. Lightwave Technology, vol. LT-5, pp. 154-162, Jan. 1987, H. Goto, "Photonic time-division switching technology," Technical Digest, Topical Meeting on Photonic Switching, pp. 132-134, Mar. 1987. In the prior art, optical write gates, bistable devices and optical read gates are often employed in such systems. The invention of optical memory cells, optical shift registers and optical serial-to-parallel converters will provide system designers with alternative approaches in designing optical time-division switching systems.
It is presently anticipated that optical time slot interchangers will play an important role in optical switching systems such as self-routing optical switching systems and optical ring switching systems. In these switching systems, the use of optical time slot interchangers will simplify the design of the systems and improve their performance.